Induction welding is a form of welding that uses electromagnetic induction to heat a portion or portions of a metal part or parts as the portion or the portions of the metal part or parts are advanced. The heated portion or portions, for example, the opposing edges of a metal sheet, are welded together by applying a force between the inductively heated portion or portions, for example, to form a tubular product, in an ambient atmosphere or a controlled environment such as an inert gas or vacuum.
Electric resistance welding (ERW) is a form of welding that uses resistance heating to heat a portion or portions of a metal part or parts as the portion or the portions of the metal part or parts are advanced. The heated surfaces are welded together by applying a force between the resistively heated portion or portions, for example, the opposing edges of a metal sheet, in an ambient atmosphere or a controlled environment such as an inert gas or vacuum to form a tubular product.
High frequency solid state power supplies used in induction or resistance welding processes can also be used in other heating processes, for example, induction annealing (heat treatment) processes where a metal workpiece or workpiece zone, such as a previously formed weld seam, requires heat treatment. The induction coil and the magnetically coupled workpiece heat treatment zone form an electric load circuit with dynamically changing load characteristics during the annealing process.
U.S. Pat. No. 5,902,506 (the '506 patent), which is incorporated herein by reference in its entirety, discloses a high frequency forge welding or annealing power supply system using variable reactors in a load matching apparatus.
It is one objective of the present invention to provide a high frequency forge welding or annealing power supply system with improved variable reactors over that disclosed in U.S. Pat. No. 5,902,506 that provide a high frequency power supply system with a closely regulated output.